Follow blockchain research across journals, conferences, and preprint repositories.
9,005 results · page 307 of 376
Aljosha Judmayer, Nicholas Stifter, Katharina Krombholz, Edgar Weippl
No abstract is available for this record.
Giulia Fanti, Shaileshh Bojja Venkatakrishnan, Surya Bakshi, Bradley Denby · 7 authors
Bitcoin and other cryptocurrencies have surged in popularity over the last decade. Although Bitcoin does not claim to provide anonymity for its users, it enjoys a public perception of being a privacy preserving financial system. In reality, cryptocurrencies publish users' entire transaction histories in plaintext, albeit under a pseudonym; this is required for transaction validation. Therefore, if a user's pseudonym can be linked to their human identity, the privacy fallout can be significant. Recently, researchers have demonstrated deanonymization attacks that exploit weaknesses in the Bitcoin network's peer-to-peer (P2P) networking protocols. In particular, the P2P network currently forwards content in a structured way that allows observers to deanonymize users. In this work, we redesign the P2P network from first principles with the goal of providing strong, provable anonymity guarantees. We propose a simple networking policy called Dandelion which provides quasi-optimal, network-wide anonymity, with minimal cost to the network's utility. We also discuss practical implementation challenges and propose heuristic solutions.
LI Zichen,LIU Boya,WANG Peidong,YANG Yatao
To ensure the wireless communication security of the reader and tag in the Radio Frequency Identification(RFID) system,based on domestic public key cryptography algorithm SM2 and introducing zero knowledge proof idea,this paper proposes a two-way authentication protocol.Then security and efficiency analysis are given.The formal analysis is made by using BAN logic.Results show that the two-way authentication of the proposed protocol is completed in the case that reader and tag just interact twice,and has high safety and communication efficiency.
Béla Gipp, Corinna Breitinger, Norman Meuschke, Joeran Beel
Manuscript submission systems are a central fixture in scholarly publishing. However, with existing systems, researchers must trust that their yet unpublished findings will not prematurely be disseminated due to technical weaknesses and that anonymous peer reviewers or committee members will not plagiarize unpublished content. To address this limitation, we present CryptSubmit - a system that automatically creates a decentralized, tamperproof, and publicly verifiable timestamp for each submitted manuscript by utilizing the blockchain of the cryptocurrency Bitcoin. The publicly accessible and tamperproof infrastructure of the blockchain allows researchers to independently verify the validity of the timestamp associated with their manuscript at the time of submission to a conference or journal. Our system supports researchers in protecting their intellectual property even in the face of vulnerable submission platforms or dishonest peer reviewers. Optionally, the system also generates trusted timestamps for the feedback shared by peer reviewers to increase the traceability of ideas. CryptSubmit integrates these features into the open source conference management system OJS. In the future, the method could be integrated at nearly no overhead cost into other manuscript submission systems, such as EasyChair, ConfTool, or Ambra. The introduced method can also improve electronic pre-print services and storage systems for research data.
Arpita Nayak, Kaustubh Dutta
Blockchain is a technology that is based on Bitcoin cryptocurrency. It is a technology for decentralizing transaction and managing data. Immense research and deep thinking has gone into conceptualizing blockchain since the time it was first showcased by Satoshi Nakamoto in 2008. The growing interest among researchers and technologists is the central attribute of blockchain that provides a high level of security, anonymity and data integrity without any intervention from third party who is in control of the transactions. Here in this study we have carried out through a well-defined study with the sole aim of collecting all relevant research areas and technologies on Blockchain Technology. With Blockchain becoming future in transactions in financial sector, it also comes with its own burden of risks. But since it has the potential to revolutionize the existing technology, it feels right to take the plunge[1].
Christian Badertscher, Sandro Coretti, Chen-Da Liu-Zhang, Ueli Maurer
Commitment schemes that admit zero-knowledge proofs for relations among committed values are known as commit-and-prove functionalities or notarized envelopes. An important role in this context play equality proofs among commitments. They appear in various contexts of multi-party computation, circuit satisfiability or inclusion proofs. Using commit- and-prove functionalities admitting equality, we investigate blackbox constructions of commit-and-prove functionalities admitting more complex relations. Typically, these constructions have to create commitments to additional values to achieve a certain level of soundness. An important efficiency measure is the number of such additional commitments. We prove that, for the natural and quite general class of 3-round public-coin zero-knowledge protocols, implementing the inequality relation, or any of the relations NAND, NOR, or XOR, essentially requires at least 2n additional commitments in order to achieve a soundness of 2-n. A folklore protocol shows that this bound is tight for inequality.
Olivier Blazy, Philippe Gaborit, Julien Schrek, Nicolas Sendrier
In this paper we give the first blind signature protocol for code-based cryptography. Our approach is different from the classical original RSA based blind signature scheme, it is done in the spirit of the Fischlin approach [9] which is based on proofs of knowledge. To achieve our goal we consider a new tool for zero-knowledge (ZK) proofs, the Concatenated Stern ZK protocol, which permits to obtain an authentication protocol for concatenated matrices. A signature is then obtained from the usual Fiat-Shamir heuristic. We describe our blind signature protocol for cryptography based on Hamming metric and show how it can be extended to rank based cryptography. The security of our blind protocol is based on the security of a trapdoor function for the syndrome decoding problem: the CFS signature scheme for Hamming distance and on the more recent RankSign protocol for rank metric. We give proofs in the random oracle model (ROM) for our blind signature scheme, which rely on the Syndrome Decoding problem. The parameters we obtain for our protocol are practical for rank metric (200kBytes) for the signature length and 15kBytes for public key size) and a little less practical for Hamming distance.
Wided Boubakri, Walid Abdallah, Noureddine Boudriga
5G mobile communication is being designed as heterogeneous network where different platforms, several technologies, and various cell sizes are deployed to fit specific requirements in terms of data rates and latency. The heterogeneity nature of this network will lead to new security issues and threats, especially when the number of deployed mobile devices become very important. In this paper, we propose a simple PKI certificate based access control scheme that is implemented on a multi-layer communication architecture designed for 5G networks. In addition, we establish a scalable authentication and handover schemes that can ensure security within the network. To this purpose, we define various types of certificates with different features and utilization. The authentication scheme is based on zero knowledge proof (ZKP) and is used to achieve secure device registration procedure before generating authorization certificates that will be used to enable secure device-to-device communication. We use simulation work to assess the efficiency of our scheme in terms of total overhead and average latency. Performance evaluation results show that our scheme is more scalable than existing authentication and handover schemes.
Jinchuan Chen, Yunzhi Xue
In recent years, data is becoming the most valuable asset. There are more and more data exchange markets on Internet. These markets help data owners publish their datasets and data consumers find appropriate services. However, different from traditional goods like clothes and food, data is a special commodity. For current data exchange markets, it is very hard to protect copyright and privacy. Moreover, maintaining data services requires special IT techniques, which is a difficult job for many organizations who own big datasets, such as hospitals, government departments, planetariums and banks. In this paper, we propose a decentralized solution for big data exchange. This solution aims at cultivating an ecosystem, inside which all participators can cooperate to exchange data in a peer-to-peer way. The core part of this solution is to utilize blockchain technology to record transaction logs and other important documents. Unlike existing data exchange markets, our solution does not need any third-parties. It also provides an convenient way for data owners to audit the use of data, in order to protect data copyright and privacy. We will explain the ecosystem, and discuss the technical challenges and corresponding solutions.
Haruka Ito, Masanori Hirotomo, Youji Fukuta, Masami Mohri · 5 authors
No abstract is available for this record.
Adriano Di Luzio, Alessandro Mei, Julinda Stefa
Distributed financial systems are radically changing the way we do business and spend our money. Ripple, in particular, is unique in its kind. It is built on consensus and trust among its users and it allows to exchange both fiat currencies and goods over its network. It does so by storing the accounts of its users, their balances, and all the transactions in a distributed ledger, publicly accessible. In this paper we perform an in-depth study of the Ripple exchange system and its public distributed ledger. We analyze payments, the structure of payment paths, and the role of the entities in the system such as Gateways (the equivalent of banks) and Market Makers. We also analyze the internal stream of events and show that Ripple relies on a surprisingly small number of active validators, raising concerns on the actual robustness and fairness of the system. Moreover, we consider the degree of anonymity that Ripple is able to guarantee. By examining the first three years of Ripple history (more than 500 GB worth of data), we show that even approximate information on a single payment can uncover, with incredible accuracy, the entire financial life of the user. For example, anyone who overhears our order of a Latte at our favourite bar can easily get complete and unlimited access to our balance, our previous and future payments, our monthly income, as well as critical information about the places where we shop and the people we trust.
Christopher Natoli, Vincent Gramoli
Most blockchain systems are forkable in that they require participants to agree on a chain out of multiple possible branches of blocks. In this paper, we identify a new form of attack, called the Balance attack, against these forkable blockchain systems. The novelty of this attack consists of delaying network communications between multiple subgroups of nodes with balanced mining power. Our theoretical analysis captures the tradeoff between the network delay and the mining power of the attacker needed to double-spend in the GHOST protocol with high probability. We quantify our analysis in the settings of the Ethereum testnet of the R3 consortium where we show that a single machine needs to delay messages for 20 minutes to double spend while a coalition with a third of the mining power would simply need 4 minutes to double spend with 94% of success. We experiment the attack in our private Ethereum chain before arguing for a non-forkable blockchain design to protect against Balance attacks.
Hoang Giang, Wee Keong Ng
Traditional cloud storage has relied almost exclusively on large storage providers, who act as trusted third parties to transfer and store data. This model poses a number of issues including data availability, high operational cost, and data security. In this paper, we introduce a system that leverages blockchain technology to provide a secure distributed data storage with keyword search service. The system allows the client to upload their data in encrypted form, distributes the data content to cloud nodes and ensures data availability using cryptographic techniques. It also provides the data owner a capability to grant permission for others to search on her data. Finally, the system supports private keyword search over the encrypted dataset.
Daniel de Melo Pimentel
This work show an avaliation about the performance of the application of Group Signature technique in Bitcoin system and a study about the anonymity and auditory. The Bitcoin’ goal is provide a virtual currency and an anonymous online transaction system. However, recent researches show that can be to break the anonymity of transactions through the chronological traceability technique in the Bitcoin transactions and analysis of network addresses. As a result of breaking anonymity of Bitcoin transactions, users’ privacy and all Bitcoin ecosystem are affected negatively. For this reason, in this work, it was proposed to include Group Signatures techniques in the Bitcoin system to increasing of anonymity in Bitcoin transactions but with audity possibility in accept time, more or less 10 minutes. The Group Signature generate a lot of dinstinct groups to dinstinct Bitcoin transactions. After to include the Group Signature technique in a modified version of Bitcoin system, we evaluated this technique in Bitcoin system through experiment in simulations. Through the experiments and statistic analysis, it was found that the approach of including the Group Signature is feasible for implementation in Bitcoin system with small groups, 500 clients. For the all cases analyzed, it was verified that the use of Group Signature in Bitcoin transactions increase the anonymity. Therefore, it was verified that the performance of Bitcoin transactions with Group Signature technique show a delay in nearly 50% less than current Bitcoin system whitout this technique. Nevertheless, in small groups with Group Signature get a better anonymity level and audity, but in big groups with more than 500 clients this technique not is good because the transactions time is over.
Val A. Red
Existing distributed ledger implementations – specifically, several blockchain implementations – embody a cacophony of divergent capabilities augmenting innovations of cryptographic hashes, consensus mechanisms, and asymmetric cryptography in a wide variety of applications. Whether specifically designed for cryptocurrency or otherwise, several distributed ledgers rely upon modular mechanisms such as consensus or smart contracts. These components, however, can vary substantially among implementations; differences involving proof-of-work, practical byzantine fault tolerance, and other consensus approaches exemplify distinct distributed ledger variations. Such divergence results in unique combinations of modules, performance, latency, and fault tolerance. As implementations continue to develop rapidly due to the emerging nature of blockchain technologies, this paper encapsulates a snapshot of sensor and internet of things (IoT) specific implementations of blockchain as of the end of 2016. Several technical risks and divergent approaches preclude standardization of a blockchain for sensors and IoT in the foreseeable future; such issues will be assessed alongside the practicality of IoT applications among Hyperledger, Iota, and Ethereum distributed ledger implementations suggested for IoT. This paper contributes a comparison of existing distributed ledger implementations intended for practical sensor and IoT utilization. A baseline for characterizing distributed ledger implementations in the context of IoT and sensors is proposed. Technical approaches and performance are compared considering IoT size, weight, and power limitations. Consensus and smart contracts, if applied, are also analyzed for the respective implementations’ practicality and security. Overall, the maturity of distributed ledgers with respect to sensor and IoT applicability will be analyzed for enterprise interoperability.
Alfonso de la Rocha Gómez-Arevalillo, Panos Papadimitratos
International audience
Chengjun Cai, Xingliang Yuan, Cong Wang
Emerging decentralized storage services such as Storj and Filecoin show promise as a new paradigm for data outsourcing. These services tie cryptocurrency to personal storage resources and leverage blockchain technology to ensure data integrity in distributed networks. Compared to current cloud storage, they are expected to be more scalable, cost effective, and secure. In addition to the features above, strong guarantees of data privacy are seriously desired due to today's prevalent data leak and abuse incidents. However, simply using end-to-end encryption limits the search capability and thus will degrade the user experience. In this paper, we propose an encrypted decentralized storage architecture that can support trustworthy and private keyword search functions. We start from searchable encryption to achieve search on encrypted data. Yet, only adopting this primitive is not sufficient to address particular threats in our target decentralized service model. Service peers would maliciously return incorrect results, while user peers would fraudulently refuse to pay service fees. To resolve those threats, we devise specific secure data addition and keyword search protocols to enable client-side verifiability and blockchain based fair judgments on the search results. For practical considerations, we integrate an efficient dynamic searchable encryption scheme to our protocols as an instantiation to lower the blockchain overhead. Our security and performance analysis indicates the advance of the proposed architecture.
Maya Mohan, M. K. Kavitha Devi
No abstract is available for this record.
Wei Xin, Tao Zhang, Chengjian Hu, Cong Tang · 6 authors
The increasing popularity of blockchain-based cryptocurrencies has made scalability a primary and urgent concern. Compared with the completely open, uncontrolled public blockchain system, private blockchain can provide better access control management. This paper proposes an architecture for distributed private blockchain. At the same time, we propose three strategies to improve the scalability of private blockchain: optimization of block construction, block size and time control optimization, and transaction security mechanism optimization. This system also redesigns the format of the trading, block structure and the way how system constructs blocks, makes it more suitable for the requirements of the private blockchain. From experiment results, we show that our system achieves better performance and scalability without compromising security guarantees.
I-Hsun Chuang, Bing-Jie Guo, Jen-Sheng Tsai, Yau-Hwang Kuo
Internet of Things (IoT) is an emerging network technology applied to provide various services in our daily life. Generally, IoT environments are composed of numerous heterogeneous devices with constrained resource. The limited capability of IoT devices makes it impractical to perform traditional security mechanisms, and thus IoT services are usually vulnerable to all kinds of security threats, such as impersonation and forgery attacks. Moreover, the inflexible protection provided by these security mechanisms leads to inefficiency because different services haves diverse requirements. To provide IoT services suitable security protection, Multi-graph Zero-knowledge-based Authentication System (M-ZAS), which is not only light-weight but also high-adaptive, is proposed. Compared to traditional authentication mechanisms as well as other Zero-knowledge-proof (ZKP) methods such as GMW-ZKP, M-ZAS provides higher performance and better security protection. In addition, M-ZAS has lower transmission overheads than GMW-ZKP does. Considering relevant contexts as parameters, M-ZAS provides adaptive protection to fulfill what users actually need. Experiment results show that M-ZAS is 3 times faster than GMW-ZKP and even 7 times than traditional authentication mechanisms in IoT devices. Also, M-ZAS reduces 3 times network traffic than GMW-ZKP. Thus, the proposed M-ZAS is the most practical authentication system in IoT environments.
Deepak K. Tosh, Sachin Shetty, Xueping Liang, Charles Kamhoua · 6 authors
The blockchain technology has emerged as an attractive solution to address performance and security issues in distributed systems. Blockchain's public and distributed peer-to-peer ledger capability benefits cloud computing services which require functions such as, assured data provenance, auditing, management of digital assets, and distributed consensus. Blockchain's underlying consensus mechanism allows to build a tamper-proof environment, where transactions on any digital assets are verified by set of authentic participants or miners. With use of strong cryptographic methods, blocks of transactions are chained together to enable immutability on the records. However, achieving consensus demands computational power from the miners in exchange of handsome reward. Therefore, greedy miners always try to exploit the system by augmenting their mining power. In this paper, we first discuss blockchain's capability in providing assured data provenance in cloud and present vulnerabilities in blockchain cloud. We model the block withholding (BWH) attack in a blockchain cloud considering distinct pool reward mechanisms. BWH attack provides rogue miner ample resources in the blockchain cloud for disrupting honest miners' mining efforts, which was verified through simulations.
Haseeb Ahmad, Licheng Wang, Haibo Hong, Jing Li · 7 authors
No abstract is available for this record.
Qi Xia, Emmanuel Boateng Sifah, Abla Smahi, Sandro Amofa · 5 authors
Disseminating medical data beyond the protected cloud of institutions poses severe risks to patients’ privacy, as breaches push them to the point where they abstain from full disclosure of their condition. This situation negatively impacts the patient, scientific research, and all stakeholders. To address this challenge, we propose a blockchain-based data sharing framework that sufficiently addresses the access control challenges associated with sensitive data stored in the cloud using immutability and built-in autonomy properties of the blockchain. Our system is based on a permissioned blockchain which allows access to only invited, and hence verified users. As a result of this design, further accountability is guaranteed as all users are already known and a log of their actions is kept by the blockchain. The system permits users to request data from the shared pool after their identities and cryptographic keys are verified. The evidence from the system evaluation shows that our scheme is lightweight, scalable, and efficient.
Alessandro Chiesa, Michael A. Forbes, Nicholas Spooner
Many seminal results in Interactive Proofs (IPs) use algebraic techniques based on low-degree polynomials, the study of which is pervasive in theoretical computer science. Unfortunately, known methods for endowing such proofs with zero knowledge guarantees do not retain this rich algebraic structure. In this work, we develop algebraic techniques for obtaining zero knowledge variants of proof protocols in a way that leverages and preserves their algebraic structure. Our constructions achieve unconditional (perfect) zero knowledge in the Interactive Probabilistically Checkable Proof (IPCP) model of Kalai and Raz [KR08] (the prover first sends a PCP oracle, then the prover and verifier engage in an Interactive Proof in which the verifier may query the PCP). Our main result is a zero knowledge variant of the sumcheck protocol [LFKN92] in the IPCP model. The sumcheck protocol is a key building block in many IPs, including the protocol for polynomial-space computation due to Shamir [Sha92], and the protocol for parallel computation due to Goldwasser, Kalai, and Rothblum [GKR15]. A core component of our result is an algebraic commitment scheme, whose hiding property is guaranteed by algebraic query complexity lower bounds [AW09,JKRS09]. This commitment scheme can then be used to considerably strengthen our previous work [BCFGRS16] that gives a sumcheck protocol with much weaker zero knowledge guarantees, itself using algebraic techniques based on algorithms for polynomial identity testing [RS05,BW04]. We demonstrate the applicability of our techniques by deriving zero knowledge variants of well-known protocols based on algebraic techniques, including the protocols of Shamir and of Goldwasser, Kalai, and Rothblum, as well as the protocol of Babai, Fortnow, and Lund [BFL91].